U.S. patent number 6,170,320 [Application Number 09/058,254] was granted by the patent office on 2001-01-09 for method of introducing an additive into a fluid system, especially useful for leak detection, as well as an apparatus for leak detection and a composition useful for leak detection.
This patent grant is currently assigned to Mainstream Engineering Corporation. Invention is credited to Dwight D. Back, Lawrence R. Grzyll, Joseph Mayer, Robert P. Scaringe.
United States Patent |
6,170,320 |
Scaringe , et al. |
January 9, 2001 |
Method of introducing an additive into a fluid system, especially
useful for leak detection, as well as an apparatus for leak
detection and a composition useful for leak detection
Abstract
An additive is introduced into a fluid system and dissolved in a
carrier fluid which is immiscible or slightly miscible in the fluid
system, wherein the carrier fluid is subsequently removed from the
fluid system. This method can be used to detect leaks, wherein an
on-off UV light source, such as xenon light, can be used to detect
the leak visually.
Inventors: |
Scaringe; Robert P. (Rockledge,
FL), Grzyll; Lawrence R. (Merritt Island, FL), Back;
Dwight D. (Melbourne, FL), Mayer; Joseph (Indian Harbor
Beach, FL) |
Assignee: |
Mainstream Engineering
Corporation (Rockledge, FL)
|
Family
ID: |
25145537 |
Appl.
No.: |
09/058,254 |
Filed: |
April 10, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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788780 |
Jan 24, 1997 |
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Current U.S.
Class: |
73/40.7; 252/67;
252/964; 436/3; 73/40.5R; 73/592 |
Current CPC
Class: |
G01M
3/20 (20130101); G01M 3/228 (20130101); G01M
3/38 (20130101); F25B 2500/222 (20130101); Y10S
252/964 (20130101) |
Current International
Class: |
G01M
3/22 (20060101); G01M 3/00 (20060101); G01M
3/38 (20060101); G01M 3/20 (20060101); G01M
003/04 (); G01M 003/20 () |
Field of
Search: |
;252/964,67,301.19
;73/40,40.5,592,40.7 ;436/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Skoog, Douglas A. and West, Donald M., Principles of Instrumental
Analysis, Second Edition, Saunders College, 1980, Figure 5-2, p.
116. .
van der Waal, G., Improving the Performance of Synthetic Base
Fluids with Additives, J. Synth. Lubr., vol. 4, No. 4, pp. 267-282,
(1987)..
|
Primary Examiner: Wu; Shean C.
Attorney, Agent or Firm: Evenson, McKeown, Edwards &
Lenahan, P.L.L.C.
Parent Case Text
This application is a division of application Ser. No. 08/788,780,
filed Jan. 24, 1997, now abandoned.
Claims
What is claimed is:
1. A method of introducing an additive into a system comprising a
system fluid, the additive comprising at least one compound,
comprising the steps of
dissolving the additive in a carrier fluid, wherein the carrier
fluid is immiscible or slightly miscible in the system fluid,
delivering the additive and the carrier fluid into the system,
and
removing the carrier fluid from the system fluid, leaving the
additive dissolved in the system fluid.
2. The method of claim 1, further comprising the step of delivering
an amount of the additive into the system in concentrations of up
to the solubility limit of the additive in the system fluid.
3. The method of claim 1, wherein the additive comprises at least
one compound which is soluble in the system fluid and the carrier
fluid, and has fluorescent properties.
4. The method of claim 1, wherein the additive comprises at least
one organic compound which emits color in the visible spectrum.
5. The method of claim 1, wherein the additive comprises at least
one fluorescent compound and at least one organic compound which
emits color in the visible spectrum.
6. The method of claim 1, wherein the system fluid comprises PAG,
POE, mineral oil or AB.
7. The method of claim 1, wherein the carrier fluid comprises
alcohol.
8. The method of claim 1, wherein the carrier fluid comprises at
least one of ethanol, methanol, and 2-propanol.
9. The method of claim 1, wherein the additive comprises a molecule
comprising at least one cyclic group, said molecule comprising
atoms selected from the group consisting of C, H, halogens, S, N,
and O.
10. The method of claim 1, wherein the additive comprises an
organo-metallic compound.
11. The method of claim 1, wherein the additive comprises an
inorganic compound.
12. The method of claim 1, wherein the additive is selected from
the group consisting of coumarin and derivatives thereof, where G
represents groups comprising at least one of C, H, halogens N, and
S, and j greater than or equal to 0: ##STR7##
13. The method of claim 1, wherein the additive is selected from
the group consisting of phenylnaphthylamines, where R.sub.1,
R.sub.2, and R.sub.3 are groups comprising at least one of C, H,
halogens, N, S, and O in cyclic or acyclic structures: ##STR8##
14. The method of claim 1, wherein the additive is selected from
the group consisting of diphenylamines, where R.sub.4 and R.sub.5
are groups comprising at least one of C, H, halogens, N, S, and O
in cyclic or acyclic structures: ##STR9##
15. The method of claim 1, wherein the additive is selected from
the group consisting of benzothiazolines, where R.sub.6, R.sub.7,
R.sub.8 and R.sub.9 are groups comprising at least one of C, H,
halogens, N, S, and O in cyclic or acyclic structures:
##STR10##
16. The method of claim 1, wherein the additive is selected from
the group consisting of benzothiazoles, where R.sub.10 and R.sub.11
are groups comprising at least one of C, H, halogens, N, S, and O
in cyclic or acyclic structures: ##STR11##
17. The method of claim 1, wherein the additive is an additive
selected from the group consisting of anti-oxidation, anti-wear,
anti-friction, dispersion improvement, and viscosity index
improvement additives.
18. A leak detection method, comprising the steps of introducing a
compound selected from the group consisting of organo-metallic
compounds comprising at least one metal and at least one cyclic or
acyclic structure comprising atoms selected from the group
consisting of C, H, N, S, and O, wherein the at least one cyclic or
acyclic group optionally includes at least one attached cyclic or
acyclic structure comprised of atoms selected from the group
consisting of C, H, halogens, N, S, and O into a refrigeration
system comprising a fluid system, and causing the compound to
fluoresce at any point in the system where there is a leak wherein
the step of introducing comprises dissolving the compound in a
carrier fluid, delivering the compound and the carrier fluid into
the system, and removing the carrier fluid from the system
fluid.
19. The method of claim 18, wherein the step of introducing the
compound into the system is effected in concentration up to the
solubility limit of the compound in the system fluid.
20. The method of claim 18, wherein the system fluid comprises PAG,
POE, mineral oil or AB.
21. The method of claim 17, wherein the carrier fluid comprises
alcohol.
22. The method of claim 17, wherein the carrier fluid comprises at
least one of ethanol, methanol and 2-propanol.
23. A leak detection method comprising the step of introducing a
compound capable of fluorescing into a refrigeration system having
a system fluid, and causing the compound to fluoresce at any point
in the system where there is a leak, wherein the compound is
soluble in the system fluid and comprises at least one of
phenylnaphthylamines: ##STR12##
where R.sub.1, R.sub.2, and R.sub.3 are groups comprising at least
one of C, H, halogens, N, S, and O in cyclic or acyclic structures;
dialkyldiphenylamines: ##STR13##
where R.sub.4 and R.sub.5 are groups comprising at least one of C,
H, halogens, N, S, and O in cyclic or acyclic structures;
organometallic compounds comprising molecular groups comprising at
least one metal and at least one cyclic or acyclic structure
comprising atoms selected from the group consisting of C, H, N, S,
and O, wherein the at least one cyclic group optionally has at
least one attached cyclic or acyclic structure comprised of C, H,
halogens, N, S, and O; benzothiazolines: ##STR14##
where R.sub.6, R.sub.7, R.sub.8 and R.sub.9 are groups comprising
at least one of C, H, halogens, N, S, and O in cyclic or acyclic
structures; and benzothiazoles: ##STR15##
where R.sub.10, and R.sub.11 are groups comprising at least one C,
H, halogens, N, S, and O in cyclic or acyclic structures wherein
the step of introducing comprises dissolving the compound in a
carrier fluid, delivering the compound and the carrier fluid into
the system, and removing the carrier fluid from the system
fluid.
24. The method of claim 23, wherein the step of introducing the
compound into the system is effected in concentrations of up to the
solubility limit of the compound in the system fluid.
25. The method of claim 23, wherein the system fluid comprises PAG,
POE, mineral oil or AB.
26. The method of claim 21, wherein the carrier fluid comprises
alcohol.
27. The method of claim 21, wherein the carrier fluid comprises at
least one of ethanol, methanol and 2-propanol.
28. A method of detecting leaks in a refrigeration system
comprising a fluid system, comprising the steps of introducing a
fluorescing compound dissolved in a carrier fluid into the fluid
system, wherein the carrier fluid is immiscible or slightly
miscible in the system fluid, delivering the dissolved fluorescing
compound and the carrier fluid into the fluid system, and detecting
the leak with a UV lamp.
29. The method of claim 28, further comprising the step of removing
the carrier fluid from the system fluid.
30. The method of claim 29, wherein the carrier fluid comprises
alcohol.
31. The method of claim 29, wherein the carrier fluid comprises at
least one of ethanol, methanol and 2-propanol.
32. The method of claim 28, wherein the UV lamp is a xenon flash
tube.
33. The method of claim 32, wherein the xenon flash tube comprises
a quartz glass.
34. The method of claim 32, wherein the xenon flash tube is filled
with a xenon gas mixture at a pressure of less than about 4
atmospheres.
35. The method of claim 32, wherein the xenon flash tube comprises
a trigger circuitry means for obtaining an adjustable or a preset
flash rate.
36. The method of claim 35, wherein the means produces a flash rate
from about 4 flashes per second to about 1 flash every four
seconds.
37. The method of claim 32, wherein the xenon flash tube comprises
a filter glass with a high degree of internal transmittance in the
180 to 390 nm ultraviolet wavelength range.
38. The method of claim 32, wherein the xenon flash tube comprises
an ultraviolet flash pulse circuit.
39. The method according to claim 1, further comprising the step of
detecting a leak in the system with a flashing UV lamp.
40. The method according to claim 39, the flashing UV lamp, a xenon
flash tube, a trigger circuitry means for obtaining an adjustable
or a preset flash rate and a filter glass.
41. The method according to claim 40, wherein the xenon flash tube
comprises an ultraviolet flash pulse circuit.
42. The method according to claim 40, wherein the xenon flash tube
comprises an UV flash pulse circuit.
43. The method according to claim 40, wherein the mean produces a
flash rate from about 4 flashes per second to about 1 flash every
four seconds.
44. The method according to claim 40, wherein the filter is applied
directly to the xenon flash tube.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention is related to a method of introducing an
additive into a fluid system, as well as to a method for detecting
leaks and an apparatus and composition useful for leak
detection.
Daylight visible and ultraviolet fluorescent dyes have been used to
detect leaks in refrigeration systems utilizing fluorocarbon
refrigerants and refrigerant oils. Typically, these dyes are
introduced into the refrigeration system, and at the site of the
leak, the leaking refrigerant, oil and dye are detected under
normal or UV light.
More specifically, a leak-detecting trace fluid, which is generally
a fluorescence (powdered) dye material dissolved in an oil or
petroleum fraction carrier, is introduced into the refrigeration
system. The fluorescent dye material is carried throughout the
system, and at the location of a leak, the refrigerant, oil, and
fluorescent dye material leak into the atmosphere. The refrigerant
is subsequently vaporized, leaving an oil residue containing the
fluorescent dye material. Application of a UV light to this area
results in the illumination of the oil/fluorescent dye
material.
U.S. Pat. No. 1,915,965 discloses a leak detector method for a
compression refrigeration system. Daylight visible compounds, such
as methyl violet, crystal violet, auramine B, rhodamine E, etc. are
introduced into such systems as leak detectors.
U.S. Pat. No. 4,249,412 discloses a UV fluorescent dye composition
comprising water, a nonionic surfactant, a 1.0 wt. % sodium
fluorescein and a semi-synthetic thickening agent. This fluorescent
dye composition is sprayed on the external surfaces of a system
where the bubbles formed by the leak fluoresce under UV light.
Other prior art examples include U.S. Pat. No. 4,369,120, which
discloses anthraquinone blue dyes for use as visual leak detectors
of refrigerants, refrigerant oils, and mixtures thereof; U.S. Pat.
No. 4,758,366, which discloses a UV fluorescent dye composition
comprising a polyhalogenated hydrocarbon refrigerant, a
refrigeration oil, or a mixture thereof, with a fluorescent dye;
U.S. Pat. No. 5,149,453, which discloses a UV fluorescent dye
composition comprising an effective amount of a fluorescent, alkyl
substituted perylene dye combined with a refrigerant oil and a
polyhalogenated hydrocarbon refrigerant; U.S. Pat. No. 5,357,782,
which discloses a UV fluorescent dye composition comprising an
optical brightener mixed with either mineral oil, polyalkylene
glycol or polyol ester refrigeration lubricant; U.S. Pat. No.
5,167,140, which discloses a method of introducing a fluorescent
dye solution into a system with an atomizing mist infuser, wherein
four different formulas for the fluorescent dye solution are
disclosed, wherein the dye solution is a fluorescent dye mixed with
an appropriate refrigerant oil; WO 92/07249, which discloses a
method and a sensor system for detecting hydrocarbon-containing
fluids by fluorescent detection, wherein additives used in
hydrocarbon-based fluids, such as gasoline, heating oils and motor
oils, can fluoresce, and can be used to detect and locate the
source of ground water contamination from gasoline and oil storage
tanks using a fluorescent sensor which detects the presence of
fluorescing materials such as Coumarin 153.
Furthermore, U.S. Pat. No. 5,440,919, discloses a method of
introducing a UV fluorescent dye additive into a closed
refrigeration system by placing the fluorescent dye on a swatch of
material installed in a desiccant bag which is placed in a
dehydrator or filter (i.e. filter-dryer) of the refrigeration
system. The swatch is capable of releasing as well as adsorbing the
dye. The refrigerant and system lubricant flow through the
dehydrator and are then mixed with the fluorescent dye, thereby
allowing the fluorescent dye to be carried throughout the system.
Although this system allows the introduction of the fluorescent dye
into the system without requiring the use of a carrier oil, it also
requires that the dehydrator or filter-dryer of the system be
changed in order to introduce the dye into the system.
Generally speaking, the standard industry method of introducing
daylight visible or fluorescent dyes into a refrigerant oil, has
been to dissolve the dye in the refrigeration oil and to introduce
this mixture into the system. There are however currently several
different types of oils that are used in refrigeration systems. For
example, polyalkylene glycol (PAG), polyol ester (POE),
alkylbenzene (AB) and mineral oils are all used in current systems
and some of these oils (or their additives) are incompatible with
one another in concentrations as low as 1%. This means that a
service technician must carry an inventory of all different types
of fluorescent dye mixtures, i.e. one for each oil type.
An even greater problem with the conventional approach is that the
technician must first determine which type of oil is used in the
system which is being checked for leaks, as often, the technician
is called upon to repair a leak in a system which has not been
previously serviced and in which the oil used is unknown. This
presents a significant problem. We have recognized that a more
universal fluorescent leak check solution which is compatible with
all potential lubricants and delivery method is needed to simplify
leak detection in refrigeration systems.
The type of daylight visible or fluorescent material used for leak
detection is also critical because the additives used in oils can
interact with the material or the material could directly and
negatively affect the properties of the oil or refrigerant.
Although the quantity of material used for fluorescent leak
detection is generally small, on the order of a few percent by
weight of oil or less, a material can adversely affect the
properties or performance of the oil or refrigerant to which it is
added. In addition, conventional fluorescent materials have not
always maximized visible light emission from UV excitation with
respect to the amount of fluorescent material added.
Another drawback to current leak detection techniques is that
conventional fluorescence leak detectors have used a very bright
mercury vapor lamp with a UV filter. Commercial UV fluorescent leak
detection devices also use halogen light sources. Other suitable UV
light sources are disclosed Skoog, et al., Principles of
Instrumental Analysis, Saunders College, 1980, Figure 5-2, p. 116,
which lists components and materials for spectroscopic instruments
and lists several light sources, including a xenon lamp, as a
source of visible light.
Flashing UV light has been used for various applications in the
past. Typically these applications use excited xenon in a light
tube to provide continuous light or to provide UV energy for
chemical curing reactions, such as in dental reconstruction. Up
until our present invention, however, flashing UV light has not
been recognized as beneficial for leak detection.
For example, U.S. Pat. No. 4,279,254 discloses a UV light used on
medical patients to radiate the skin. The UV electrical light
circuit, which is not battery operated, counts pulse flashes in
order to automatically shut off and avoid over-exposure as a safety
measure; U.S. Pat. No. 4,112,335 discloses a rapid pulse UV light
apparatus in which a UV light source is fed as a high frequency
pulse into a high pressure (3 atmosphere) xenon light tube to cure
epoxy resin tooth caps; U.S. Pat. No. 4,550,275 discloses a high
efficiency pulse light source as a xenon light source to excite
lasers; U.S. Pat. No. 5,185,552 discloses a vacuum UV light source
which provides a high output UV light source using low pressure
hydrogen or deuterium in a hollow tube at wave lengths below 180
mm; U.S. Pat. No. 4,229,658 discloses a dental xenon light
apparatus which supplies UV and visible light and is used to cure
tooth restoration materials by focusing the light on a small area
of a tooth; and U.S. Pat. No. 5,043,634 discloses a pulsed light
source using a pulsed xenon light tube coupled with a phosphorus
coating which emits different colors of visible light as a
navigational aid.
Industries in which leak detection is important have not recognized
that leaks can be detected by administering a fluorescing material
to any system using a carrier fluid injected at any pressure,
regardless of oil type, and detected using a UV lamp. Moreover, we
are not aware that anyone prior to our invention recognized that a
visible dye can be used in addition to a UV fluorescing material to
further facilitate visualization and location of leaks. Our
recognitions provide a much simplified and advantageous method of
leak detection.
An object of the present invention, is to provide a more effective
method of introducing an additive into a system to avoid the need
for a system specific carrier oil and the time consuming process of
replacing the filter to introduce the additive.
Another object of the present invention is to provide a method of
introducing an additive into a system which will not degrade the
performance of the system.
Another object of the present invention is to provide a method of
introducing conventional fluorescent or daylight visible dyes or
mixtures thereof into a fluid system for leak detection.
Still another object of the present invention is to provide a
method of introducing a conventional material with heretofore
unrecognized UV-fluorescing properties into a refrigeration oil or
lubrication system using a carrier solvent, in which the solvent is
later separated from the oil or lubricant after use as a
carrier.
The materials having fluorescence properties in accordance with the
present invention are usually solid at room temperature, and are
selected from a group of commercially available compounds, some of
which are already used in the oil manufacturing industry as
additives to promote the performance characteristics of oil. Many
of these fluorescent materials are also soluble in lubricants and
oils, whether the oil is petroleum-derived (mineral) or synthetic
but up until now their ability to fluoresce has not been
appreciated.
A yet further object of the present invention is to select a
carrier solvent which will evaporate from the compressor oil, so
that it can be removed by adsorption with a filter-dryer of a
refrigeration system. The solvent should generally be immiscible or
slightly miscible in the refrigeration system oil or lubricant, so
that it can be removed from the system by adsorption using
appropriately sized filter-dryers containing an adsorbent which
adsorbs the solvent similar to those used in conventional
refrigeration system design. The solvent should also be compatible
with the lubricants and refrigerants currently used by the HVAC
industry. A carrier solvent for the additive is removed after being
used as a carrier in accordance with the present invention and thus
greatly reduces concerns of both material and refrigerant
incompatibility of the carrier solvent with the system.
Another object of the present invention is to provide daylight
visible or fluorescent additives which are soluble in both the
solvent carrier as well as the various types of refrigerant oils,
i.e. synthetic or petroleum-derived. Solubility is desirable for at
least two reasons. First, the additive is dissolved in the solvent
alone for delivery into the refrigeration or air conditioning
system. If the additive were insoluble in the solvent, the additive
could precipitate or form a residue. As a result, inadequate
amounts of additive would be delivered into the system or insoluble
residues could clog key system components, such as the expansion
device, and cause operational problems. Second, once adequate
amounts of the additive are delivered into the system, the additive
must be soluble in the specific refrigerant lubricant used in the
system, allowing the additive to travel with the lubricant
throughout the system to the location of the leak. The
refrigerant/lubricant/additive mixture then leaks into the
atmosphere at the site of the leak, leaving a lubricant/additive
residue at the site which can be detected by visible light or by
application of UV light to the area.
Furthermore, another object of the present invention is to overcome
the problems and disadvantages of conventional leak detecting light
sources, which include power consumption and poor detection
capabilities, by providing a high-efficiency xenon flashing light
source. We have found that the advantage in using a flashing light
instead of, for example, a continuous light source, is that it
makes the fluorescing material more noticeable. That is, the
flashing light provides the operator with a continuous comparison
between a leaking region with fluorescence and the same region with
normal ambient light, thereby making the fluorescing material
appear to flash and easier to detect.
Normally, xenon lights inherently flash at a frequency so that the
light is easily perceptible as continuous to the human eye.
According to the present invention, however, the light has an
adjustable on-off duty cycle, wherein the light may be off for 0.5
seconds or more. As a result of the longer off-time, such units use
significantly less power and make battery powered units
practical.
These objects have been achieved in accordance with the present
invention by a method in which an additive is introduced with a
carrier fluid into a refrigeration system to detect system
leaks.
An advantage of the present invention is that it can also use known
fluorescent dye materials. Instead of dissolving the material in an
oil or petroleum-based carrier which has to be compatible with the
oil used in the system, however, our invention is based on the
recognition that the fluorescent material can be of a type which is
dissolvable in a solvent carrier which does not remain in the
system. The fluorescent materials and solvents of the present
invention are, to great advantage, universally soluble and, at the
same time, fluorescent in petroleum-based and synthetic oils and
lubricants.
According to a currently preferred embodiment, the carrier fluid is
a non-oil carrier, such as an alcohol. When the carrier is an oil
or lubricant, as used in the past, additives such as fluorescing
materials, which may or may not have performance enhancing
properties, can have very low solubility. In contrast thereto,
alcohol generally has a high solubility for such fluorescing
materials of the present invention, and therefore, will dissolve
the additive with a comparatively smaller volume as compared to the
volume of oil or lubricant which might be necessary to dissolve the
same quantity of additive.
The present invention also advantageously uses additives with
natural fluorescent characteristics which are not damaging to the
performance of the oil, lubricant or refrigerant. Moreover, with
the use of our invention and its general principles, the
incorporation of certain additives into the system actually
benefits the performance, wear, stability, and/or life of the oil
or lubricant when the additive has anti-wear, anti-oxidant,
viscosity improving, and/or dispersing properties.
According to the present invention, the extent to which the
additives are used is essentially only limited by the solubility of
the additive in the system fluid. The concentration of additive
should, generally speaking, be limited to an amount below which
precipitation occurs, because precipitation of the additive may be
detrimental to the fluid system and performance.
Yet another advantage of the present invention is the use of
mixtures of fluorescent materials and daylight visible dyes which,
when used together, provide enhanced visual detection of the
leakage and/or alter the fluorescent color of the fluorescent
material to enhance detection of the mixture.
In accordance with the present invention, a method is utilizable by
which an additive and a solvent carrier can be introduced into a
refrigerant system, regardless of the system pressure and
temperature or whether the system is or is not open to the
environment. The solvent carrier can then be removed from the
system by adsorption in a filter normally present in the system,
leaving only the dissolved additive in the system oil or
lubricant.
In summary, we have discovered, among other things, that the
carrier solvent should have the following properties to obtain the
benefits of our invention:
1. The solvent must be capable of dissolving the additive;
2. The solvent should ideally, but need not, be immiscible in all
possible lubricants so that the solvent does not dissolve in the
lubricant and become difficult to remove or reduce the lubrication
properties of the lubricant;
3. The solvent should be compatible with all materials and fluids
in the system; and
4. The solvent should be rapidly adsorbed by the molecular sieve,
activated alumina, and/or carbon filter-dryers used in typical
refrigeration systems so that the solvent can be removed from the
system thereby leaving only the additive dissolved in the
lubricant.
Xenon tubes used as a light source according to the present
invention, advantageously produce a full spectrum of light very
efficiently, without the generation of significant heat. This light
can then be filtered to remove the visible and IR frequencies,
leaving only the ultraviolet spectrum. The result is an
intermittent, intense light of long wave ultraviolet black light or
UV-A, typically in the 180 nm to 390 nm wavelength range of the
electromagnetic spectrum.
Generally, the light sources for detecting fluorescing materials
require a filter to filter-out visible light. Without a filter, the
illumination of the fluorescing material is much less noticeable.
Typically, the filter is a glass filter because the conventional
continuous light source generates sufficient heat to damage
inexpensive filters. According to the present invention, however,
the xenon filter cooling effect advantageously results from a duty
cycle in which there is a relatively slow on/off frequency.
Xenon light sources are generally in the form of xenon arc lamps,
which burn continuously, or xenon flash tubes which are typically
flashed at very high frequencies to approximate (i.e., appear to
the naked eye as) a continuous light source. However, the present
invention employs a xenon light which is turned on at a low
frequency, with a very pronounced on and off cycle. Such xenon
flashing lights generate significantly less heat and thus avoid
potential safety concerns, reduce fabrication costs, and allow for
the use of inexpensive plastic or glass lenses or the application
of a UV filter material directly on the xenon bulb. Their
utilization in leak detection of the type involved herein provides
advantages not heretofore recognized.
Instead of using a continuous beam of UV light, it was found that,
by introducing an intermittent (on/off duty cycle) UV light, the UV
sensitive fluorescing material is more noticeable. The on/off UV
light source allows a repeated comparison between the fluorescing
leak indicator and the background, much like a flashing warning
light is more noticeable to a driver at night. We also found that
an adjustable flashing frequency allows the user to adjust the
frequency to suit the user according to ambient light conditions.
The intermittent light also advantageously consumes significantly
less power, making possible the use of light-weight, low-cost,
portable, battery-powered units.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description when considered in conjunction with the accompanying
drawings wherein.
FIG. 1 is an overall schematic of a xenon flash the circuit used in
connection with the detection method of the present invention;
FIG. 2 is a schematic diagram of a first embodiment of a xenon lamp
circuit used in connection with the detection method of the present
invention;
FIG. 3 is a schematic diagram of a second embodiment of a xenon
lamp circuit used in connection with the detection method of the
present invention;
FIG. 4 is a schematic diagram of a third embodiment of a xenon lamp
circuit used in connection with the method of the present
invention; and
FIG. 5 is a schematic representation of a method of introducing an
additive into a conventional fluid system with a UV light source
being directed at an area with a leak and being observed.
DETAILED DESCRIPTION OF THE INVENTION
According to a presently preferred embodiment of the present
invention, ethanol has been identified as a suitable carrier fluid.
We introduced ethanol into the oil of an actual system to verify
that ethanol would vaporize in a conventional vapor compression
system such as a heat pump, air conditioning or refrigeration
system, would not remain in the oil, but instead would be adsorbed
in the system filter-dryer within a reasonably short time period.
The amount of ethanol introduced on the low pressure side of the
compressor was 2 grams (or 1% of the oil weight). The ethanol
vaporized from the oil and was adsorbed by the filter-dryer after
several hours of operation. Therefore, ethanol was found to be a
suitable carrier fluid to combine with an additive that is both
soluble in ethanol and in all possible refrigeration oils for the
reasons stated above.
For example, with regard to additive solubilities, we have measured
the solubilities of fluorescent compounds N-phenyl-1-naphthylamine
and N-phenyl-2-naphthylamine, which happen to fluoresce under UV
light and are known oil and lubricant antioxidants, in several oils
and alcohols. The former is soluble to as much as 30 weight percent
in methanol, ethanol, and isopropanol, whereas the latter is
soluble to about 6 weight percent in methanol and ethanol.
N-phenyl-1-naphthylamine is also soluble to about 25 weight percent
in POE oil, about 10 weight percent in AB oil, and about 3 weight
percent in mineral oil.
Although ethanol is the currently preferred solvent, alcohols such
as methanol and 2-propanol (isopropyl alcohol or isopropanol) can
also be used. An alcohol such as ethanol which is immiscible in
oil, however, is preferable because the alcohol is then more easily
separated from the oil in the vapor compression cycle. Although
ethanol is immiscible in oil, methanol is only slightly miscible in
oil, and 2-propanol is completely miscible. The present invention
contemplates the use of such miscible and slightly miscible
alcohols, but with the understanding that they take longer to
separate from the oil and reduce the lubrication properties of the
oil. Therefore, even though ethanol is the preferred carrier fluid
for use with current refrigerants and oils used in refrigeration
compressors today, other alcohols such as 2-propanol and methanol
can still be used alone or in combination with ethanol as a carrier
fluid for the additive according to the present invention.
Additives which dissolve in a carrier fluid such as methanol,
ethanol, and isopropanol, must also be compatible with the
refrigerants, lubricants, and construction materials used in the
system, because these additives remain in the system after the
carrier fluid has been removed by the filter-dryer. It is important
that the additive which remains in the system not affect the
performance properties of the system fluid. One measure of this
effect is through a wear test, more specifically ASTM method D2670.
For example, wear tests performed according to ASTM D2670 for a 0.1
weight percent composition of N-phenyl-1-naphthylamine, a
fluorescent additive also known in the oil industry as an
anti-oxidant, in POE oil, show no effect on the wear properties of
the base oil. It has been shown by van der Waal, G., Improving the
Performance of Synthetic Base Fluids with Additives, J. Synth.
Lubr., Vol. 4, No. 4, pp. 267-282 (1987), that alkylated
diphenylemines and alkylated phenyl-2-naphthylamines can actually
improve the wear properties of oils and lubricants, as measured by
ASTM standard D2670.
The alcohol (i.e., methanol, ethanol, and isopropanol) or
alcohol-additive solution can be introduced anywhere in the
vapor-compression system. Even if introduced directly into the
compressor oil, the alcohol-oil concentration is less than 1% and
will not affect the lubrication properties of the oil, especially
as the alcohol quickly vaporizes and is adsorbed within hours by
the filter-dryer. As described above, experiments have verified
that ethanol does vaporize and travel through the system where it
becomes adsorbed in the filter-dryer (i.e. molecular sieve, carbon
or activated alumina adsorption bed) of the system. The result is
that the additive dissolved in the alcohol is transferred into the
system by the alcohol. Therefore, after the alcohol-additive
mixture is introduced into the system, the additive is dissolved in
the oil lubricant and the alcohol is adsorbed by the filter-dryer.
The additive, which is dissolved in the oil, is then transported
through the system with the oil.
We have found that many more potential additive materials, covering
several families of organic, inorganic and organometallic compounds
having fluorescent properties, are available for the above purpose
than was previously recognized. We found that the most intense and
useful fluorescence behavior is achieved by organic compounds which
contain aromatic functional groups and low-energy .pi.-.pi.*
transition levels. In addition, compounds containing aliphatic and
alicyclic carbonyl structures or highly conjugated double-bond
structures can also fluoresce. Usually, the more rigid the
molecular structure, the more likely the compound is to fluoresce.
Fluorene (.alpha.-diphenylenemethane), a rigid biphenyl compound,
will fluoresce when impure and is soluble in alcohol, benzene, and
ether. Some common benzene compounds, including chlorobenzene,
bromobenzene, anisole, and benzoic acid, also fluoresce at 300-400
nm. Other fluorescing materials used as indicators in various
solutions include fluorescein, .beta.-naphthol, and eosin.
Organic compounds can also be chelated to certain metals to produce
highly fluorescent organo-metallic structures, which are usually
more rigid than their precursors. For example, 8-hydroxyquinoline
exhibits increased fluorescence when complexed with zinc and is
soluble in alcohol. Flavonol fluoresces when exposed to Zr or Sn
and is generally soluble in organic solvents. Alizarin garnet R
will fluoresce when chelated with Al and F. Consequently, metals
which may be present in a refrigeration system with a solvent
carrier can also react to form a fluorescent chelated compound by
the introduction of the organic chelating agent into the
system.
Additionally we have made the surprising discovery that certain
compounds already used as additives by the oil industry have
fluorescing capabilities, and these compounds could be used as
fluorescent additives without any perceived concerns about
degrading the performance of the oil base. Numerous additives are
often added to lubricants and oils for various reasons, such as for
anti-oxidation, anti-wear, anti-friction, dispersion improvement,
and viscosity index improvement. Such compounds include
benzothiazolines, benzothiazoles, benzotriazoles,
aminoalklyphenothiazines, aminophenylbenzothiazoles,
phenothiazines, phenols, 1,3,4-thiadiazoles and alkyl, aryl or
alkylaryl derivatives of these compounds. Specific compounds
include 2-aminobenzothiazole, benzothiazole,
N-phenyl-1-naphthylamine, 2,2-dimethylbenzothiazoline,
bis(benzothiazoline), benzotriazole, methylene bis(dibutyl
dithiocarbamate), 2,6-di-tert-butyl-4-methylphenol, or
2,5-dimercapto-1,3,4-thiadiazole.
Furthermore, additives, compounds and derivatives containing other
organic groups such as alkyl, amino, alkenyl, alkylnyl, cycloalkyl,
aryl, or substituted aralkyl are also incorporated into lubricating
and other working fluids, such as hydraulic fluids, by grafting the
compound to a polyolefin backbone such as polyethylene or
polypropylene (see U.S. Pat. No. 4,708,810; U.S. Pat. No.
4,948,524; U.S. Pat. No. 5,147,569; and U.S. Pat. No. 5,271,856)
many of which contain components known to fluoresce. Additionally,
organo-metallic compounds such as molybdenum
dialkylphosphorodithioate and Zinc octyldithio-phosphate are also
used because of their anti-wear, anti-oxidation and anti-friction
properties.
Inorganic compounds such as zinc sulfide and cadmium sulfide, are
also known fluorescent compounds used in lamp tubes and television
screens. These materials and other inorganic compounds could also
be administered into fluid systems by way of a carrier fluid and
used for fluorescent leak detection.
Phenylnaphthylamines and diphenylamines, and their derivatives
containing alkyl, aryl, or alkylaryl groups, are known
anti-oxidants and oxidation stability additives for petroleum-based
or synthetic lubricating oils (see U.S. Pat. No. 3,944,492; U.S.
Pat. No. 4,064,059; U.S. Pat. No. 4,157,970; U.S. Pat. No.
4,179,386; U.S. Pat. No. 4,320,018; and U.S. Pat. No. 5,523,008).
Examples of phenylnaphtylamines include N-phenyl-1-naphthylamine,
N-phenyl-2-naphthylamine, N-(4-cumylphenyl)-1-naphthylamine,
p-tert-dodecylphenyl-2-naphthylamine. Examples of diphenylaminies
and dialkylphenylamines include diphenylamine,
dioctyldiphenylamine, and didecyldiphenylamine.
Phenylnaphthylamines and dialkyldiphenyl amines are generally used
as antioxidants in oils in concentrations of up to about 5% by
weight. These compounds are also generally soluble in alcohols,
mineral oils, and synthetic oils. The use of benzothiazole and its
derivatives has been taught for the detection of enzymatic activity
in U.S. Pat. No. 5,424,440. N-phenyl-1-naphthylamine has been used
in studies of the membrane structure of chloroplasts using
fluorescent probes (see Acros Organics catalog, Fisher Scientific,
1995-1996). Heretofore, however, these compounds have not been used
as fluorescing materials for leak detection.
Several coumarin compound derivatives such as
2,3,6,7-tetrahydro-9(trifluoromethyl)-1H,5H,11H-[1]benzopyrano[6,7,8,ij]qu
inolizin-11-one (coumarin 153) also fluoresce and are sometimes
also incorporated in gasoline and oils as additives. Another
fluorescent coumarin compound,
7-(2H-naphtho[1,2-d]-triazol-2-yl)-3-phenyl-coumarin, is used as an
optical brightener and sometimes also as a brightener and additive
for thermoplastic materials. This compound is also soluble in
alcohol and oils.
Table 1 summarizes some conventional dyes which were found to be at
least slightly soluble in ethanol and oils, and which fluoresce
when excited by UV light. Table 2 lists examples of compounds which
are commonly used as additives in lubricants and oils, but which
have not been recognized as advantageous additives for fluorescent
leak detection.
TABLE 1 CONVENTIONAL CHEMICAL DYES STRUCTURE/NAME KNOWN SUPPLIER
Coumarin 153 2,3,6,7-tetrahydro-9(trifluoromethyl)- Aldrich
Chemical Co. 1H,5H,11H-[1]benzopyrano-[6,7,8,ij]- Milwaukee, WI
quinolizin-11-one Leucopure
7-(2H-naphtho[1,2-D]triazol-2-yl)-3-phenyl- Clariant Corporation
coumarin 4000 Monroe Road Charlotte, NC 28205 Basonyl Brilliant
Yellow C.sub.22 H.sub.24 N.sub.3 O.sub.2.CH.sub.3 O.sub.4 S,
Methine family BASF Corporation Colorants 3000 Continental Drive N.
Mount Olive, NJ 07828-1234 Fluoretrack II not available Formulabs.
Inc. P. O. Box 1869 Piqua, OH 45356 FWT Red not available
Formulabs, Inc. P. O. Box 1869 Piqua, OH 45356
TABLE 2 ADDITIVE NAME KNOWN SUPPLIER N-phenyl-1-naphthylamine
Aldrich Chemical Co., Milwaukee WI N-phenyl-2-naphthylamine Aldrich
Chemical Co., Milwaukee WI benzothiazole Aldrich Chemical Co.,
Milwaukee WI 2-aminobenzothiazole Aldrich Chemical Co., Milwaukee
WI 2,2-dimethyl benzothiazoline ChemService, West Chester, PA
diphenylamine Aldrich Chemical Co., Milwaukee WI
Since the ring structures of these compounds are generally
responsible for the fluorescing properties, substituted derivatives
of these structures would be expected by those skilled in the art
to have similar fluorescing properties. The general structure of
the cyclic compounds summarized in Tables 1 and 2 which can
fluoresce with UV excitation include coumarin compounds and
derivatives thereof with the following structure: ##STR1##
where G comprises groups comprising C, H, halogens, N, and/or S and
j greater than or equal to O; phenylnaphthylamine compounds and
derivatives thereof: ##STR2##
where R.sub.1, R.sub.2, and R.sub.3 are groups comprising any
combination of C, H, halogens, N, S, and/or O in cyclic or acyclic
structures; dialkyldiphenylamine compounds and derivatives thereof:
##STR3##
where R.sub.4 and R.sub.5 are groups comprising any combination of
C, H, halogens, N, S, and/or O in cyclic or acyclic structures;
benzothiazoline compounds and derivatives thereof: ##STR4##
where R.sub.6, R.sub.7, R.sub.8 and R.sub.9 are cyclic or acyclic
groups comprising C, H, halogens, N, S, and/or O; and benzothiazole
and derivatives thereof: ##STR5##
where R.sub.10 and R.sub.11 are cyclic or acyclic groups comprising
C, H, halogens, N, S, and/or O.
Other heterocyclic and multiple-cyclic structures which can
fluoresce under UV excitation include naphthalene, quinoline,
isoquinoline, purine and carbazole, and derivatives thereof
comprising C, H, halogens, S, N, and/or O. Daylight visible dyes
such as rhodamine B, C.sub.28 H.sub.31 ClN.sub.2 O.sub.3, crystal
violet (or methyl violet), and anthraquinone with the following
structure: ##STR6##
are soluble in alcohol and contain multi-cyclic components
comprising C, H, halogens, N, and O.
Some of these compounds are yellow, however, which is not a highly
visible color. These compounds can, however, be mixed with another
dye which emits color in the visible spectrum and not fluorescent,
and which is soluble in both refrigerant lubricants and solvents in
order to obtain a more noticeable color. For example, yellow
fluorescing materials can be mixed with Sudan Blue visible dye to
create a mixture which will illuminate green under UV light.
The mixture of additive and carrier fluid may be introduced into a
refrigerant system by connecting a reservoir containing the mixture
in a bypass between the high pressure side and the low pressure
side of the refrigeration system compressor is shown in FIG. 5. By
introducing flow through the bypass, the mixture in the bypass
reservoir is driven into the low pressure side of the system, and
having done so, the bypass can be disconnected.
Consequently, the leak check fluid (i.e. the additive and carrier
fluid) does not have to be oil specific, because the alcohol
solvent is compatible with all oils potentially present in such
systems, and in any case, is quickly removed by adsorption by the
filter-dryer of the system. This novel method is contrary to the
current practice of dissolving a dye in a lubricating oil which may
not be compatible with another unknown oil in the system as noted
above.
A low (on-off) frequency xenon lamp coupled with a UV filter is
used with great advantage to provide the UV light. A conventional
high pressure (up to as much as 4 atmosphere, quartz glass UV lamp
is preferably used (such as manufactured by Amglo Kemlite
Laboratories, Inc.). Quartz glass is preferred because of high UV
transmissivity. Because the duty cycle for such a slow-flashing
(i.e., flashing in the sense of turning the light completely on and
off) light allows for greater cooling, the UV filter can either be
applied directly to the quartz bulb surface or a thin glass (rather
than a thick glass) or plastic filter can be used. In a preferred
embodiment, the flash rate is from about 4 flashes per second to
about 1 flash every four seconds.
In a currently preferred embodiment, the electrical circuit is
advantageously operated from a battery power source to provide a
high voltage D.C. power. A fundamental electrical circuit as seen
in FIG. 1 comprises a high voltage section A which provides
approximately 300-500 volts from a conventional battery power
supply (not shown) and a trigger section B which intermittently
provides approximately 6,000 to 11,000 volts (from the battery
power source) to trigger the xenon flash tube C and cause the xenon
light to flash. The frequency of the trigger voltage provided by
the circuit B is, however, adjustable in order to adjust the on/off
duty cycle of the UV light.
To specifically implement the above described high voltage and
trigger voltage circuits A and B, three different embodiments of
adjustable duty cycle xenon lamp circuits are discussed in further
detail below with reference to FIGS. 2, 3 and 4.
The xenon flash tube circuit in FIG. 1 includes a high voltage DC
to DC inverter, a trigger circuit and a xenon flash tube.
The inverter consists of a 12 volt source from a battery which is
applied to an oscillator circuit which produces a high frequency 12
volt pulse fed into a step up transformer. The output of the
transformer, typically 450 volts, is rectified to direct current
using a voltage tripler circuit.
The high voltage of approximately 450 volts is connected to each of
the two terminals on the xenon tube. This high voltage is also used
to fire a SCR (Silicon Controlled Rectifier), which presents a
pulse to a high voltage trigger coil at a rate determined by an RC
constant and the firing voltage of the neon tubes found across the
gate and anode of the SCR. The output of the trigger coil is
connected to the center trigger wire of the xenon tube. When the
SCR fires, a 450 volt pulse is sent to the trigger coil which steps
up the voltage to 6,000 to 11,000 volts depending on the coil used.
The resulting voltage applied to the xenon tube causes the tube to
light and inherently flash.
Referring now to FIG. 2, the high voltage section A comprises a
low-voltage audio amplifier 1, powered by 12 VDC power source. The
amplifier 1 is used in a stable multivibrator mode with a frequency
of above 1000 kilohertz as determined by capacitor 2 and variable
resistor 5. The output at pin 5 at the amplifier 1 is a square wave
that drives a transformer 7 via a capacitor 6. Transformer 7 is an
audio transformer connected with a 4 or 8 ohm secondary as the
primary. The 1200 ohm secondary delivers 450 volts peak to peak to
diode 8, 9, 12 and capacitor 10, 11, 13 comprising of a
voltage-tripler circuit which produces a 450 volt output at point
"B".
For the xenon flash tube trigger section B, a 450 VDC voltage is
applied to capacitor 16 through resistors 14, 15, the latter being
variable. By varying the resistance of resistor 15, the charge time
for full voltage on capacitor 16 can be varied to control the flash
cycle time of the flash tube 20. The xenon flash tube 20 has the
power supply voltage of 450 volts across its terminals, but
requires a trigger voltage greater than 6000 volts to the trigger
anode to cause the xenon tube 20 to fire. The trigger circuit
consists of the capacitor 16, SCR 17, neon lamp 18, and trigger
transformer 19. The capacitor 16 charges until the neon lamp 18 has
approximately 90 volts across its terminals and breaks down,
creating a conductive path between the gate and the anode of SCR 17
which then fires the SCR providing a conductive path between the
anode and cathode. The full voltage of the capacitor 16 is passed
through the SCR 17 and to the primary of the transformer 19. A
stepped up secondary voltage of 10,000 volts to the flash tube
anode results and fires the xenon flash tube 20. The recharge cycle
begins again.
In the embodiment of FIG. 3, the circuit uses a pot core
transformer 4 which performs two functions. Coil N1 provides a
feedback to the driving transistor 3 configured in a modified
Hartly oscillator. NPN transistor 3 oscillates at a frequency based
on resistor 1, capacitors 2, 6 and switches a pulsed 12 VDC to the
primary (N2 winding) of the transformer 4. Coil N2 provides the
primary winding of a transformer. The voltage is stepped up in
secondary coil N3 of the transformer and is rectified and filtered
by diode 5 and capacitor 6 producing a output voltage to the flash
tube trigger circuit at point "B".
A 275 VDC voltage is applied to the capacitor 7 through resistor 8
and 9. By changing the resistance of the resistor 9, the full
voltage charge time on the capacitor 7 can be varied to control the
flash recycle time of the flash tube 13. The flash tube 13 has a
power supply voltage of greater than 275 volts across its terminals
but requires a trigger voltage greater than 6,000 volts to the
trigger anode to cause the xenon tube 13 to fire. The trigger
circuit consists of the capacitor 7, SCR 10, neon lamp 11, and
transformer 12. Capacitor 7 charges until neon lamp 11 has
approximately 90 volts across its terminals and breaks down,
creating a conductive path between the gate and the anode of SCR 10
that fires the SCR. The full voltage of the capacitor 7 is passed
through the SCR 10 and to the primary of transformer 12 resulting
in a stepped up secondary voltage of at least 6,000 volts to the
flash tube anode which fires the xenon flash tube 13. The recharge
cycle begins again.
In the embodiment of FIG. 4, the integrated circuit (IC) is a 555
timer circuit 1, powered by 12 VDC, used in a stable multivibrator
mode. The frequency output of IC 1 is determined by potentiometer
resistor 5. The IC 1 provides a pulsed voltage to the base of NPN
transistor 8 which switches a pulsed 12 VDC to the primary of setup
transformer 9. The voltage is stepped up in the secondary winding
of the transformer and is then rectified and filtered by diode 10
and capacitor 11 producing an output voltage to the flash tube
trigger circuit at point "B".
A greater than 275 VDC voltage is applied to capacitor 12 through
resistors 13, 14, the latter being variable. By changing the
resistance of variable resistor 14, the full voltage charge time on
capacitor 12 can be varied to control the flash recycle time of the
flash tube 18. The flash tube 18 has the power supply voltage of
greater than 275 volts across its terminals but requires a trigger
voltage greater than 6,000 volts to the trigger anode to cause the
xenon tube 18 to fire. The trigger circuit consists of capacitor
12, SCR 15, neon lamp 16, and trigger transformer 17. Capacitor 12
charges until neon lamp 16 has approximately 90 volts across it's
terminals and breaks down, creating a conductive path between the
gate and the anode of SCR 15 that fires the SCR providing a
conductive path between the anode and cathode. The full voltage of
capacitor 12 is passed through SCR 15 and to the primary of
transformer 17 resulting in a stepped up secondary voltage of 6,000
volts to the flash tube anode which fires the xenon flash tube 18.
The recharge cycle begins again.
Although the invention has been described and illustrated in
detail, it is to be clearly understood that the same is by way of
illustration and example, and is not to be taken by way of
limitation. The spirit and scope of the present invention are to be
limited only by the terms of the appended claims.
* * * * *